1. Field of the Invention
The present invention relates to an ink jet recording apparatus and a method, and more particularly to a correction technique when a nozzle causes deflected ejection.
2. Description of the Related Art
After an ink jet head mounted on an ink jet recording apparatus is started to be used, a nozzle which has fallen into a non-ejecting state (non-ejecting nozzle) due to clogging or failure may occur. If a non-ejecting nozzle occurs in an ink jet recording apparatus of a single path method, a “streak” appears in a drawn image to remarkably lower quality of the image. Thus, in an ink jet recording apparatus of the single path method, if a non-ejecting nozzle occurs, processing of reducing visibility of a streak (non-ejection correction) is performed.
FIGS. 14A to 14F are conceptual diagrams showing a basic idea of non-ejection correction.
FIGS. 14A to 14F are as follows: FIG. 14A shows schematic dot arrangement when there is no non-ejecting nozzle; FIG. 14B shows schematic visual appearance of an output image (image drawn on a medium) when there is no non-ejecting nozzle; FIG. 14C shows schematic dot arrangement when a non-ejecting nozzle occurs; FIG. 14D shows schematic visual appearance of an output image when a non-ejecting nozzle occurs; FIG. 14E shows schematic dot arrangement when non-ejection correction is performed; and FIG. 14F shows schematic visual appearance of an output image when non-ejection correction is performed.
As shown in FIG. 14D, if a non-ejecting nozzle occurs, a streak (streak of a ground color of a medium) occurs in a drawing region corresponding to the non-ejecting nozzle.
As described above, the non-ejection correction serves as processing of reducing visibility of the streak. The processing is achieved by thickening drawing with a nozzle (non-ejection correction nozzle) close to the non-ejecting nozzle as shown in FIG. 14E.
A method of thickening drawing with a non-ejection correction nozzle is known as a method of scanning an output image, a method of increasing an ejection dot diameter by enhancing an ejection signal, and the like.
As shown in FIG. 14F, performing the non-ejection correction reduces visibility of the streak to improve image quality, however, the image quality is lowered as compared with image quality when there is no non-ejecting nozzle.
A streak appearing on an image occurs due to not only non-ejection but also deflected ejection (indicating directional ejection failure of an ink droplet ejected from a nozzle).
FIGS. 15A to 15D are conceptual diagrams showing an occurrence mechanism of a streak caused by deflected ejection.
FIGS. 15A to 15D are as follows: FIG. 15A shows schematic dot arrangement when there is no deflected ejection; FIG. 15B shows schematic visual appearance of an output image when there is no deflected ejection; FIG. 15C shows schematic dot arrangement when the deflected ejection occurs; and FIG. 15D shows schematic visual appearance of an output image when deflected ejection occurs.
If deflected ejection occurs, ink is not ejected to a position where the ink should be originally ejected to cause a streak to appear in a drawn image. In addition, if deflected ejection occurs, adjacent dots overlapping too much may be visually identified as a streak (concentration of the dots becoming too high results in allowing the dots to be visually identified as a streak).
In a case where a streak occurs in an image due to deflected ejection, a nozzle in which the deflected ejection occurs (deflected ejection nozzle) is not allowed to eject ink to perform non-ejection correction (refer to FIGS. 14E and 14F). Accordingly, occurrence of the streak caused by the deflected ejection is canceled to improve image quality, however, the image quality is lowered as compared with image quality when deflected ejection does not occur (refer to FIGS. 14B and 14F).
Deflected ejection does not always constantly occur, but changes as time elapses depending on a usage manner of an ink jet head. Thus, in order to maintain always stable image quality, it is necessary to regularly detect a nozzle in which deflected ejection occurs (deflected ejection nozzle).
A method of detecting a deflected ejection nozzle is known as a method in which a test chart is drawn to analyze an image of the drawn test chart so that a deposited position of ink is measured to identify a deflected ejection nozzle by comparing with a reference position, and the like (refer to Japanese Patent Application Laid-Open No. 2011-201051, for example).
In the method above, a nozzle position is applied to the reference position set as a comparison object, that is, a deposited position of the ink with the assumption that deflected ejection does not occur is set as the reference position.